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Velamentous cord insertion is often diagnosed using an abdominal ultrasound. [3] [4] This is most successful in the second trimester, [13] however Color Doppler ultrasound [14] or transvaginal ultrasound [15] can be used in difficult cases, such as when the placenta is located
In the second trimester, a standard ultrasound exam typically includes: [12] Fetal number, including number of amnionic sacs and chorionic sacs for multiple gestations; Fetal cardiac activity; Fetal position relative to the uterus and cervix; Location and appearance of the placenta, including site of umbilical cord insertion when possible
The placenta can be defined as an organ formed by the sustained apposition or fusion of fetal membranes and parental tissue for physiological exchange. [1] This definition is modified from the original Mossman (1937) [2] definition, which constrained placentation in animals to only those instances where it occurred in the uterus.
Sadly, circumvallate placenta can occasionally result in infant death depending on the severity of the complications encountered. In other cases, circumvallate placenta can result in premature birth of infants who are otherwise healthy after being monitored in the neonatal intensive care unit for a period of time after birth.
The placenta develops once the blastocyst is implanted, connecting the embryo to the uterine wall. The decidua here is termed the decidua basalis; it lies between the blastocyst and the myometrium and forms the maternal part of the placenta. The implantation is assisted by hydrolytic enzymes that erode the epithelium.
Blood sampling may be achieved with more ease if the placenta is in the anterior position. However, if the placenta is in the posterior position, the fetus might block direct access to the umbilical cord. Once the umbilical cord is reached and the correct position of the needle is confirmed, the fetal blood is drawn.
The endometrium is central, echogenic (detectable using ultrasound scanners), and has an average thickness of 6.7 mm. During pregnancy, the glands and blood vessels in the endometrium further increase in size and number. Vascular spaces fuse and become interconnected, forming the placenta, which supplies oxygen and nutrition to the embryo and ...
Due to the fact that placental mammals and marsupials nourish their developing embryos via the placenta, the ovum in these species does not contain significant amounts of yolk, and the yolk sac in the embryo is relatively small in size, in comparison with both the size of the embryo itself and the size of yolk sac in embryos of comparable developmental age from lower chordates.